Jason Costomiris on 16 May 2008 09:39:32 -0700

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Re: [PLUG] Ubuntu Alternate installer, RAID1 & LVM

On May 16, 2008, at 8:03 AM, Matt Mossholder wrote:

> On Fri, 2008-05-16 at 07:53 -0400, Matt Mossholder wrote:
>> If not, you could always have LVM do the mirroring on /boot, rather  
>> than
>> use md.
> Please ignore this.. while LVM does support striping, it doesn't  
> support
> mirroring. Rather odd, eh?

I wouldn't say it's odd..  LVM is aimed at solving partitioning  
issues, while RAID is aimed at solving redundancy issues.

The "striping" in LVM is really JBOD, while a proper RAID setup would  
use identical sized volumes to build the redundant volume.

It makes lots of sense to actually combine the two even.

So, you stick 2 drives in a server, and put them together in RAID-1  
as /dev/md0.  Everything's cool, until you decide, "Hey, I really  
could use more space on /home".  Since you just put the filesystem  
directly on the raid device, you're stuck, unless you add drives, and  
shuffle lots of stuff around.

Instead, you designate /dev/md0 as a physical volume for LVM, then  
carve out LVM slices for your partitions.  Need to add space to /home?  
No problem.  Add another couple of drives, put them together as  
RAID-1, add them to the LVM volume group and expand the /home  

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